Stats chapter 2

Frequency Distribution

A table that shows how many observations fall into each category or class.

Frequency

The number of times a value or category occurs.

Relative Frequency

Frequency ÷ Total Number of Observations.

Percent Frequency

Relative Frequency × 100.

Cumulative Frequency

The running total of frequencies.

Range

Largest value − Smallest value.

Ordered Array

Data arranged from smallest to largest.

Class Interval

A range of values used to group numerical data.

Class Width

The size of each class interval in a frequency distribution.

Histogram

Used for numerical data; bars touch because the data are continuous.

Bar Chart

Used for categorical data; bars are separated by gaps.

Pie Chart

Shows each category as a percentage of the whole.

Pareto Chart

A bar chart arranged from highest frequency to lowest frequency.

Stem-and-Leaf Plot

Displays numerical data while preserving the original values.

Scatter Plot

Shows the relationship between two numerical variables.

Time Series Plot

Shows how data changes over time.

Contingency Table

A table showing the relationship between two categorical variables.

Row Percentage

Percentage calculated within each row.

Column Percentage

Percentage calculated within each column.

Overall Percentage

Percentage calculated using the total number of observations.

Best graph for categorical data

Bar Chart, Pie Chart, or Pareto Chart.

Best graph for numerical data

Histogram or Stem-and-Leaf Plot.

Best graph for two numerical variables

Scatter Plot.

Best graph for data over time

Time Series Plot.

Histogram vs. Bar Chart

Histogram = numerical data & touching bars; Bar Chart = categorical data & gaps between bars.

Relative Frequency Formula

Frequency ÷ Total.

Percent Frequency Formula

(Frequency ÷ Total) × 100.

Purpose of a Frequency Distribution

To organize data and show how often values occur.

Why do histogram bars touch?

Because the data are numerical and continuous.

Why do bar chart bars have gaps?

Because the categories are separate and not continuous.